The present invention relates generally to medical devices for insertion into the human or animal body and more particularly to guiding members with central lumens, particularly perfusion devices and balloons. Even more particularly, the present invention relates to a perfusion guidewire capable of delivering gas supersaturated solutions at high pressure atraumatically and bubble-free.
Various medical procedures require fluids to be delivered to specific locations within the body, typically via a fluid delivery catheter. A narrow steerable guidewire is often used to maneuver through narrow, tortuous, and/or branching body passageways. After the guidewire has been directed to the desired location, a fluid delivery catheter may be inserted over the guidewire. The guidewire is usually removed before fluid delivery begins. Alternatively, guidewires which are themselves capable of fluid delivery are also known in the art. Examples of such guidewires are disclosed in U.S. Pat. Nos. 4,964,409 and 5,322,508. Although the devices disclosed in these two patents do not appear to have been commercialized, it would appear that both would suffer from similar drawbacks in manufacturability and handling characteristics due to the manner in which the core wire is attached within each device.
Another application of such fluid delivery devices is in balloon angioplasty and similar procedures. In balloon angioplasty, a catheter equipped with a small balloon is inserted (usually over a guidewire) into an artery that has been narrowed, typically by the accumulation of fatty deposits. The balloon is then inflated to clear the blockage or lesion and widen the artery. During balloon inflation, blood flow distal to (i.e., xe2x80x9cdownstreamxe2x80x9d from) the inflated balloon may be completely or almost completely blocked.
Myocardial ischemia (i.e., a reduction in blood perfusion to the heart muscle) occurs transiently in many patients undergoing coronary angioplasty procedures, such as balloon angioplasty, directional atherectomy, rotational atherectomy, and stent deployment. The permissible duration of occlusion due to balloon inflation or other device deployment is normally determined by the severity of myocardial ischemia. Typically, evidence of severe ischemia (including patient chest pain and ECG changes) requires that the operator deflate the balloon or remove the occlusive device after approximately 60 to 120 seconds. For anatomically difficult lesions, such as type B and C lesions, longer periods of balloon inflation (or other device deployment) are frequently desirable for the first balloon inflation or other device deployment.
Autoperfusion balloon catheters can in some circumstances allow longer periods of balloon inflation. However, the blood (or other physiologic liquid) flow through such devices is frequently insufficient to provide an adequate oxygen supply to tissues distal to the angioplasty balloon or other occlusive device.
Recent advances in the generation and delivery of supersaturated oxygen solutions have made it possible to deliver greater amounts of oxygen to tissues distal to an angioplasty balloon. For example, U.S. Pat. No. 5,407,426, entitled xe2x80x9cMethod for Delivering a Gas-Supersaturated Fluid to a Gas-Depleted Site and Use Thereofxe2x80x9d and U.S. Pat. No. 5,599,296 entitled xe2x80x9cApparatus and Method of Delivery of Gas-Supersaturated Liquidsxe2x80x9d disclose various methods for the generation and delivery of supersaturated oxygen solutions.
As is described in the two above patents, the generation, transport, and delivery of supersaturated oxygen solutions may require the application of high hydrostatic pressures. Accordingly, there is a need for a high pressure device capable of infusing bubble-free fluid, which is supersaturated at high pressures (preferably with oxygen), to vessels or ducts through and beyond the central lumen of a balloon angioplasty catheter or similarly occlusive device. There is a further need for a high pressure guidewire capable of delivering such supersaturated oxygen solutions to small vessels without rupturing or otherwise damaging those vessels. The guidewire disclosed in the ""508 and ""409 patents referenced above would not be well suited to such applications for a variety of reasons. For example, the internal fluid lumens and fluid exits are not configured to eliminate bubble formation which can result from the delivery of gas supersaturated liquids. Bubble formation in the coronary arteries can be fatal. Also these devices are not designed to handle the high pressures necessary for adequate oxygen delivery while maintaining an a traumatic flow out of the device. There thus remains a need in the art for a fluid delivery device with standard guidewire handling characteristics capable of atraumatically delivering gas supersaturated fluids at high pressure into tortuous vasculature.
Accordingly, it is an object of the present invention to provide a guidewire capable of delivering perfusion fluids to a vascular site while at the same time exhibiting handling characteristics associated with existing non-perfusion guidewires so that additional education or retraining of operators is reduced or eliminated.
It is a further object of the present invention to provide a guidewire capable of delivering supersaturated solutions at high pressures to vessels or ducts atraumatically.
A preferred embodiment of the present invention meets the foregoing needs by providing a perfusion guidewire which closely matches the dimensions and physical characteristics of standard guidewires in diameter, length, flexibility, column strength, torque transfer, surface friction, kink resistance, radiopacity (i.e., opacity to x-rays), non-thrombogenicity (i.e., tendency not to promote blood clots) and bio-compatibility. A preferred embodiment of the invention includes a diffuser which provides bubblefree injection of metastable supersaturated solutions. The diffuser is provided with sleeves positioned so that the rapid flow from the diffuser is deflected axially along the device to protect vessels from rupture. A perfusion guidewire according to the present invention preferably includes four general sections: a tubular proximal segment, which comprises the greater part of the perfusion guidewire length; a transitional region which provides for attachment of the core wire such that the fluid delivery requirements are met without compromising guidewire handling; a distal diffuser segment which provides a pressure and velocity drop for the delivered fluid and serves to optimally deflect fluid flow; and a coil tip which mimics the distal functions of a standard coronary guidewire. A further aspect of the present invention includes a method of attaching a core wire to a tubular housing in a fluid delivery guidewire or other device. A preferred embodiment of the method includes forming a side hole in the tubular housing, passing an end of the core wire through the hole in the tubular housing, melting a ball on the end of the core wire, pulling the core wire to position the ball against the tubular housing and welding it in place.